1. Field of the Invention
The invention generally relates to a communication device, and more particularly, to a communication device with an antenna system having high isolation and high radiation efficiency.
2. Description of Related Art
Along with the widespread of wireless network applications and fast development of technologies, the transmission capacity and transmission rate of communication devices have been constantly increased. Thus, multi-input multi-output (MIMO) systems with multiple antennas and the ability to simultaneously transmit and receive signals have been attracting more and more attention. In other words, multi-antenna operation has become one of the future development trends. In addition, owing to the limited internal spaces of communication devices, the antennas are spaced close to each other and isolation elements are usually disposed therebetween to improve the isolation between the antennas. Generally, a conventional isolation element has an open end and captures a coupling current from a ground plane between two antennas. However, the conventional isolation element may turn into a parasitic radiation element, which may cause the radiation efficiency of the antennas to decrease.
Thereby, how to maintain the original radiation efficiency of an antenna when the isolation between the antennas in the antenna system is improved has become a major subject for a communication device with an antenna system.